Fastener driving apparatus

ABSTRACT

A fastener driving apparatus includes a power source, a control circuit, a motor, a first cylinder, a first piston, a linear motion converter, a second cylinder, a second piston, an anvil, a valve arrangement and at least one sensor. During a compression stroke, the first piston is configured to compress gas in a first cylinder to a predetermined pressure. At the predetermined pressure, the valve arrangement assumes an open position for communicating the compressed gas to the second cylinder, thereby causing the second piston to move linearly and enabling the anvil to drive the fastener into the workpiece. During a return stroke, at a predetermined position of the first piston in the first cylinder, the valve arrangement assumes the open position for communicating a vacuum created in the first cylinder to the second cylinder and thereby causing the second piston and the anvil to retract to their initial positions.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 United States Code,Section 119 on the U.S. Provisional Patent Application numbered61/208,556 filed on Feb. 25, 2009, the disclosure of which isincorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to apparatuses for drivingfasteners into workpiece, and more particularly, to a fastener drivingapparatus used as a portable hand tool.

BACKGROUND OF THE DISCLOSURE

A fastener driving apparatus is a tool used to drive fasteners, such asnails and staples into a workpiece. The fastener driving apparatus maybe used for various operations, such as making wooden walls, positioninghang sheathings over the wooden walls, fastening baseboards over a lowerportion of an interior wall and crown molding.

There are various fastener driving apparatuses known in the art. Thesefastener driving apparatuses operate utilize various means andmechanisms known in the art for their operation. For example, the priorart fastener driving apparatuses may be operated based on compressed airgenerated by an air compressor, fuel cells, electrical energy, aflywheel mechanism, and the like.

Although these fastener driving apparatuses are useful in driving thefasteners into the workpiece, such apparatuses have numerouslimitations. For example, the fastener driving apparatuses operated onthe compressed air are bulkier, non-portable and costlier due torequirement of the air compressor and associated air-lines. Fastenerdriving apparatuses operated on the fuel cells are complicated in designand are expensive. Further, the apparatuses that are operated on thefuel cells require both electrical energy and fuel. More specifically, aspark source required for combustion of the fuel derives its energy fromvarious electric energy sources such as batteries, and the like.Furthermore, the fastener driving apparatuses operated on the fuel cellsgenerate loud report and release of combustion products.

Further, the fastener driving apparatuses operated on the electricalenergy are limited to fasteners of relatively small lengths, such as oneinch or less. Further, the fastener driving apparatuses operated on theelectrical energy generate high reactionary force. The high reactionaryforce is a consequence of the comparatively longer time taken by suchfastener driving apparatuses to drive the fasteners into the workpiece.Further, the fastener driving apparatuses operated on the electricalenergy are limited in their repetition rate because of long time ittakes to drive a fastener into the work piece. Moreover, althoughfastener driving apparatuses operated by flywheels are capable ofdriving the fasteners of longer sizes very quickly, these apparatusesare bulkier in sizes and weight. Further, drive mechanisms of theseapparatuses are complicated in design, which results in a high cost ofsuch apparatuses.

Additionally, a majority of the above-mentioned fastener drivingapparatuses includes a striker mechanism for driving the fasteners intothe workpiece. The striker mechanism may be retracted to its initialposition by means of various retracting mechanisms, such as a spring, abungee and the like. Although such striker mechanisms are useful indriving the fasteners into the workpiece, these retracting mechanismshave numerous limitations. For example, the retracting mechanisms, dueto inertia associated therewith, consume significant drive energy of thefastener driving apparatuses and may prevent the fasteners from beingfully driven into the workpiece. Accordingly, these retractingmechanisms may require an increase in power to drive the fasteners intothe workpiece. Further, these retracting mechanisms reduce drive speedof the fastener driving apparatuses. Furthermore, the existingretracting mechanisms may bias the striker mechanism towards theworkpiece, causing a safety hazard for the user.

Based on the foregoing, there exists a need for a fastener drivingapparatus employing a retracting mechanism that precludes consumption ofdrive energy of the fastener driving apparatus and facilitates afastener to be fully driven into a workpiece. The fastener drivingapparatus should have the retracting mechanism capable of precludingreduction of drive speed of the fastener driving apparatus and should becapable of providing safety to a user. Further, the fastener drivingapparatus should be portable in nature and should be capable of drivingthe fastener into the workpiece in a single stroke.

SUMMARY OF THE DISCLOSURE

In view of the foregoing disadvantages inherent in the prior art, thegeneral purpose of the present disclosure is to provide a fastenerdriving apparatus that is configured to include all the advantages ofthe prior art, and to overcome the drawbacks inherent therein.

Accordingly, an object of the present disclosure is to provide afastener driving apparatus employing a retracting mechanism thatprecludes consumption of drive energy and reduction in drive speed ofthe fastener driving apparatus and facilitate a fastener to be fullydriven into a workpiece.

Another object of the present disclosure is to provide a fastenerdriving apparatus that is portable in nature and is capable of providingmore safety to a user.

Yet another object of the present disclosure is to provide a fastenerdriving apparatus that is capable of driving a fastener into a workpiecein a single stroke and is capable of increasing efficiency of thefastener driving apparatus.

Still another object of the present disclosure is to provide a fastenerdriving apparatus that is capable of minimizing reactionary forcegenerated during fastener driving operation.

In light of the above objects, a fastener driving apparatus for drivinga fastener into a workpiece is disclosed. The fastener driving apparatusincludes a power source, a control circuit, a motor, a first cylinder, afirst piston, a linear motion converter, a second cylinder, a secondpiston, an anvil, a valve arrangement and at least one sensor. Thecontrol circuit is electrically coupled to the power source. The motoris electrically coupled to the power source and is responsive to thecontrol circuit.

The first piston is reciprocally movable within the first cylinder toexecute a compression stroke and a return stroke. The first piston isconfigured to define a gas chamber within the first cylinder. The gaschamber is capable of accommodating gas therein. The first piston isoperationally coupled to the linear motion converter. The linear motionconverter is driven by the motor. The linear motion converter isconfigured to reciprocally move the first piston within the firstcylinder. The first cylinder is pneumatically connected to the secondcylinder. The second piston is reciprocally movable within the secondcylinder. The anvil is coupled to the second piston. The anvil iscapable of striking the fastener to drive the fastener into theworkpiece. The valve arrangement is operationally disposed between thefirst cylinder and the second cylinder for pneumatically connecting thefirst cylinder and the second cylinder. The valve arrangement isconfigured to define a gas passageway between the first cylinder and thesecond cylinder in an open position. Further, the valve arrangement isalso configured to block the gas passageway in a closed position. The atleast one sensor is communicably coupled to the control circuit. The atleast one sensor is configured to detect at least one position of theoperation cycle and communicate the detected position of the operationcycle to the control circuit. The control circuit is configured to stopan operation cycle of driving the fastener into the workpiece based onthe detected position by the at least one sensor.

The control circuit is configured to actuate the valve arrangement toconfigure one of the open position and the closed position based on thedetected position of the first piston.

During the compression stroke, the first piston is configured to movetowards a top dead center of the first cylinder thereby compressing thegas in the gas chamber to a predetermined pressure. Further, the valvearrangement assumes the open position at the predetermined pressure forcommunicating the compressed gas to the second cylinder. The compressedgas communicated to the second cylinder causes the second piston to movelinearly and enables the anvil to drive the fastener into the workpiece.During the return stroke, the valve arrangement assumes the closedposition and the first piston is configured to move towards a bottomdead center of the first cylinder thereby creating a vacuum in the firstcylinder between the top dead center of the first cylinder and the firstpiston. At a predetermined position of the first piston during thereturn stroke, the valve arrangement assumes the open position. The openposition of the valve arrangement causes the vacuum created in the firstcylinder to communicate to the second cylinder, thereby causing thesecond piston and the anvil to retract to initial positions of thesecond piston and the anvil.

This aspect together with other aspects of the present disclosure, alongwith the various features of novelty that characterize the presentdisclosure, are pointed out with particularity in the claims annexedhereto and form a part of this present disclosure. For a betterunderstanding of the present disclosure, its operating advantages, andthe specific objects attained by its uses, reference should be made tothe accompanying drawings and descriptive matter in which there areillustrated exemplary embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features of the present disclosure will become betterunderstood with reference to the following detailed description andclaims taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a longitudinal cross-sectional view of a fastenerdriving apparatus depicting an initial stage of an operation cycle ofdriving a fastener from the fastener driving apparatus, in accordancewith an embodiment of the present disclosure;

FIG. 2 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus depicting compression of gas in a gas chamber to apredetermined pressure, in accordance with an embodiment of the presentdisclosure;

FIGS. 3 and 4 illustrate longitudinal cross-sectional views of thefastener driving apparatus depicting rapidly expanding gas driving asecond piston and an anvil in a downward direction for driving thefastener into a workpiece, in accordance with an embodiment of thepresent disclosure;

FIG. 5 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus depicting a closed position of a valve arrangement anda first piston performing a return stroke, in accordance with anembodiment of the present disclosure;

FIG. 6 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus depicting the closed position of the valve arrangementand the first piston generating vacuum in a first cylinder, inaccordance with an embodiment of the present disclosure;

FIG. 7 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus depicting an open position of the valve arrangementcommunicating the vacuum created in the first cylinder to the secondcylinder for retracting the second piston and the anvil to their initialpositions, in accordance with an embodiment of the present disclosure;

FIG. 8 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus depicting vacuum retracted initial positions of thesecond cylinder and the anvil, in accordance with an embodiment of thepresent disclosure;

FIG. 9 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus, in accordance with another embodiment of the presentdisclosure; and

FIG. 10 illustrates a longitudinal cross-sectional view of the fastenerdriving apparatus, in accordance with yet another embodiment of thepresent disclosure.

Like reference numerals refer to like parts throughout the descriptionof several views of the drawings.

DETAILED DESCRIPTION OF THE DISCLOSURE

The exemplary embodiments described herein detail for illustrativepurposes are subject to many variations in structure and design. Itshould be emphasized, however, that the present disclosure is notlimited to a particular fastener driving apparatus as shown anddescribed. It is understood that various omissions and substitutions ofequivalents are contemplated as circumstances may suggest or renderexpedient, but these are intended to cover the application orimplementation without departing from the spirit or scope of the claimsof the present disclosure.

The terms “first,” “second,” and the like, herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another, and the terms “a” and “an” herein do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item.

The present disclosure provides a fastener driving apparatus for drivingfasteners into a workpiece. As used herein, the term “fastener” refersto, but is not limited to, a nail, a staple, and the like. Further, theterm “gas” as used herein, refers to, but is not limited to “atmosphericair”. Herein, the terms “gas” and “air” are interchangeably usedthroughout the description. Furthermore, an ‘operation cycle’ of drivinga fastener refers to steps involved in driving the fastener completelyinto a workpiece from the fastener driving apparatus. The operationcycle may also be termed as a combination of a “compression stroke” anda “return stroke” of a first piston.

The fastener driving apparatus, disclosed in the present disclosure,includes a power source, a control circuit, a motor, a first cylinder, afirst piston, a linear motion converter, a second cylinder, a secondpiston, an anvil, a valve arrangement and at least one sensor. The firstpiston is reciprocally movable within the first cylinder to execute acompression stroke and a return stroke. The first piston executes thecompression stroke and return stroke with help of the motor and thelinear motion converter. Operation of the motor is further controlled bythe control circuit. The valve arrangement is configured topneumatically connect the first cylinder and the second cylinder. Thevalve arrangement assumes one of an open position and a closed positionduring an operation cycle of driving a fastener into the workpiece. Inthe open position of the valve arrangement, the valve arrangementdefines a gas passageway allowing any communication of gas between thefirst cylinder and the second cylinder. Further, in the closed positionof the valve arrangement, the gas passageway is blocked to stop anycommunication of gas between the first and second cylinders.

During the compression stroke of the first piston in the first cylinder,the first piston is configured to move towards a top dead center of thefirst cylinder, thereby compressing gas in a gas chamber formed above anupper face of the first piston in the first cylinder to a predeterminedpressure or a predetermined stroke of the first piston. Further, thevalve arrangement assumes the open position at the predeterminedpressure or the predetermined stroke and allows the compressed gas tocommunicate to the second cylinder. The compressed gas communicated tothe second cylinder causes the second piston disposed in the secondcylinder to move linearly. The anvil is coupled to the second piston.The anvil also moves linearly with the movement of the second piston andstrikes the fastener thereby driving the fastener into the workpiece.

During the return stroke of the first piston in the first cylinder, thevalve arrangement assumes the closed position, and the first piston isconfigured to move towards a bottom dead center of the first cylinder.Movement of the first piston towards the bottom dead center of the firstcylinder creates a vacuum between the top dead center of the firstcylinder and the first piston. When the first piston reaches apredetermined position in the first cylinder during the return stroke,the valve arrangement assumes the open position. The open position ofthe valve arrangement causes the vacuum created in the first cylinder tocommunicate to the second cylinder and thereby causes the second pistonand the anvil to retract to their initial positions. Further, thefastener driving apparatus becomes ready for driving a next fastenerfrom the fastener driving apparatus. The working mechanism andconfiguration of the fastener driving apparatus of the presentdisclosure is described herein in conjunction with FIGS. 1 to 8.

Referring to FIGS. 1 to 8, longitudinal cross-sectional views of afastener driving apparatus 10 are illustrated. An operation cycle fordriving a fastener 1000 from the fastener driving apparatus 10 will bedescribed in conjunction with FIGS. 1 to 8. Referring particularly toFIG. 1, the fastener driving apparatus 10 includes a power source 100, acontrol circuit 200, a motor 300, a first cylinder 400, a first piston500, a linear motion converter 600, a second cylinder 700, a secondpiston 800, an anvil 900, a valve arrangement 2000 and a pair of sensors3002, 3004.

The power source 100 is configured to provide power for working of thefastener driving apparatus 10. The power source 100 may be arechargeable battery, a battery pack, or any other power source such asan AC power supply. The power source 100 is electrically coupled to thecontrol circuit 200. The power source 100 may be electrically coupled tothe control circuit 200 by means of wired, wireless means or any othermechanism known in the art.

The control circuit 200 is configured to actuate the power source 100for initiating the operation cycle for driving the fastener 1000.Similarly, the control circuit 200 is configured to deactivate the powersource 100 after completion of the operation cycle. The control circuit200 may be any of the various control circuits known in the art. In oneembodiment of the present disclosure, the control circuit 200 mayinclude a microprocessor, plurality of high power switching elements andcontrol circuit inputs. Further, in another embodiment of the presentdisclosure, the control circuit 200 may include a limit switch coupledto cams and linkages. Further, the control circuit 200 may be configuredto receive input signals from timers, sensors, and the like.Furthermore, the control circuit 200 may also be configured to providean output signal to an interface, a LED, and the like. Moreover, in oneembodiment of the present disclosure, the control circuit 200 mayinclude at least one low battery indicator, a pulse control of motorpower, a plurality of communication ports, a status display indicator, afault lockout protection controller, and the like. The control circuit200 is configured to control the working of the motor 300 by activatingor deactivating the power source 100.

The motor 300 is electrically connected to the power source 100. Themotor 300 may be electrically connected to the power source 100 by meansof various means and mechanisms, such as an electric wire or a magneticcoupling. The motor 300 is further responsive to the control circuit200. More specifically, the control circuit 200 is configured to directthe power from the power source 100 to the motor 300 for initiating theoperation cycle of driving the fastener such as the fastener 1000 intothe workpiece. Similarly, the control circuit 200 is configured todisconnect the power from the power source 100 to the motor 300 aftercompletion of the operation cycle. In one embodiment of the presentdisclosure, the motor 300 may include a dynamic braking system forhalting the rotations of the motor 300. Further, in one embodiment ofthe present disclosure, the fastener driving apparatus 10 may include aswitch 302 for directing and disconnecting the power from the powersource 100 to the motor 300 through the control circuit 200. Morespecifically, the switch 302 may be controlled by the control circuit200 for appropriately actuating the starting and stopping of theoperation cycle of fastener drive apparatus 10. The switch 302 may be anON/OFF switch. The motor 300 is configured to impart a reciprocatingmovement to the first piston 500 in the first cylinder 400. The motor300 provides the reciprocating movement to the first piston 500 throughthe linear motion converter 600. The linear motion converter 600 isconfigured to convert the rotational motion of the motor 300 into linearreciprocating movement of the first piston 500 within the first cylinder400.

The linear motion converter 600 is driven by the motor 300. Withoutdeparting from the scope of the present disclosure, the linear motionconverter 600 may be driven by the motor 300 through a speed reductionmechanism 4000. The speed reduction mechanism 4000 is configured toreduce the revolutions per minute (rpm) of the motor 300 depending upona required speed of reciprocating movement of the first piston 500. Inone embodiment of the present disclosure, the speed reduction mechanism4000 may be a gear reduction mechanism. The speed reduction mechanism4000 is connected to the linear motion converter 600 through a shaft4002. In the present embodiment of the present disclosure, the linearmotion converter 600 is shown as a crankshaft mechanism. Herein, thelinear motion converter 600 includes a crankshaft 602 and a connectingrod 604 connected to the crankshaft 602.

The crankshaft 602 includes a first end portion 606, a middle portion608 and a second end portion 610. The first end portion 606 of thecrankshaft 602 is connected to a body portion 1100 of the fastenerdriving apparatus 10 and the second end portion 610 is coupled to theshaft 4002 that is coupled the speed reduction mechanism 4000. The bodyportion 1100 refers to a structural framework on which variouscomponents of the fastener driving apparatus 10 may be disposed.Further, the speed reduction mechanism 4000 is coupled to the second endportion 610 of the crankshaft 602 for transmitting the rotational motiongenerated by the motor 300 to the crankshaft 602 and the connecting rod604. The connecting rod 604 is connected to the middle portion 608 ofthe crankshaft 602. An upper end portion 612 of the connecting rod 604is connected to the first piston 500. In one embodiment of the presentdisclosure, the upper end portion 612 of the connecting rod 604 isconnected to the first piston 500 by means of a piston pin (not shown).Further, a lower end portion 614 of the connecting rod is connected tothe middle portion 608 of the crankshaft 602. The lower end portion 614of the connecting rod 604 may be connected to the middle portion 608 ofthe crankshaft 602 by means of various means and mechanisms, such as anut and a bolt, a rivet, and the like.

Although, in the embodiment of the present disclosure shown in FIG. 1,the linear motion converter 600 is described in accordance with thecrankshaft mechanism, but the linear motion converter 600 may includeother arrangements, such as a slider crank arrangement, a rack andpinion arrangement, a lead screw arrangement, and the like.

Further, the first cylinder 400 of the fastener driving apparatus 10includes an upper end portion 402, a lower end portion 404 and acylinder end cap 406. The cylinder end cap 406 is configured on theupper end portion 402. The cylinder end cap 406 further includes anopening 408 configured thereon. The first cylinder 400 may have a volumethat is proportional to the amount of energy required for driving thefastener 1000 into the workpiece. In one embodiment of the presentdisclosure, for driving an 18 gage fastener, the volume of the firstcylinder 400 may be around 8 to 12 cubic inch at standard atmospherictemperature and pressure conditions.

The first piston 500 is disposed within the first cylinder 400. Thefirst piston 500 includes an upper face 502, a lower face 504, a bodyportion 506 and a check valve 508. Further, the first piston 500 isconfigured to define a gas chamber 510 within the first cylinder 400.More specifically, the first piston 500 is configured to define the gaschamber 510 between the upper face 502 of the first piston 500 and thecylinder end cap 406 of the first cylinder 400. The gas chamber 510 iscapable of accommodating gas therein. The first piston 500 is configuredto reciprocally move within the first cylinder 400 to execute thecompression stroke and the return stroke. During the compression stroke,the first piston 500 is configured to move from the lower end portion404, i.e., Bottom Dead Center (BDC) of the first cylinder 400 to theupper end portion 402, i.e., Top Dead Center (TDC) of the first cylinder400. Further, during the return stroke, the first piston 500 isconfigured to move from the upper end portion 402 (TDC) of the firstcylinder 400 to the lower end portion 404 (BDC) of the first cylinder400.

Before starting the compression stroke, the gas chamber 510 may have avolume of the gas stored therein, which is proportional to the amount ofenergy required for driving the fastener 1000 into the workpiece. In onespecific embodiment of the present disclosure, for driving the 18 gagefastener, the gas chamber 510 may have a volume of about 9 to 11 cubicinches, before starting the compression stroke at standard atmosphericpressure and temperature conditions. More specifically, in thisembodiment, for driving the 18 gage fastener, the gas chamber 510 mayhave a volume of about 10 cubic inches at standard atmospheric pressureand temperature conditions. The gas stored in the gas chamber 510 isprevented from flowing towards the lower face 504 of the first piston500, as the check valve 508 assumes the closed position.

The check valve 508 is disposed in the body portion 506. Morespecifically, the check valve 508 may be disposed on a side portion ofthe body portion 506. However, the present disclosure is not limited toa particular disposition of the check valve 508 within the body portion506. The check valve 508 is a unidirectional valve configured to allowatmospheric air to flow into the first cylinder 400 in an open position.

As shown in FIG. 1, the fastener driving apparatus 10 includes avertical actuation member 5000 for the actuation of the check valve 508.The vertical actuation member 5000 may be disposed on the body portion1100 of the fastener driving apparatus 10. More specifically, thevertical actuation member 5000 may be disposed adjacent to theconnection of the first end portion 606 of the crankshaft 602 to thebody portion 1100. The vertical actuation member 5000 includes a firstend portion 5002 and a second end portion 5004. The first end portion5002 of the vertical actuation member 5000 is connected to the bodyportion 1100. The second end portion 5004 is configured to actuate thecheck valve 508 to configure the open position of the check valve 508,when the first piston 500 reaches the lower end portion 404 of the firstcylinder 400. In one embodiment, the check valve 508 may be configuredsuch that when the crankshaft 602 rotates till 30 degrees from astarting point of the crankshaft 602, the gas chamber 510 is replenishedwith the atmospheric air. Herein, the starting point of the crankshaft602 refers that when the crankshaft 602 is at the starting point, thefirst piston 500 is at the BDC of the first cylinder 400.

In another embodiment, instead of using the check valve 508, thediameter of the lower end portion 404 of the first cylinder 400 may belarger than remaining portion of the first cylinder 400. Further, thefirst piston 500 may include O rings formed on lateral surfaces thereof.When the first piston 500 moves towards the TDC of the first cylinder400 from the BDC of the first cylinder 400, there are inlets formedbetween either sides of the first piston 500 and the lower end portion404 of the first cylinder 400. The atmospheric air enters the gaschamber 510 through the inlets. Further, during the movement of thefirst piston 500 towards the TDC, when the O rings go past the lower endportion 404, i.e., an enlarged section of the first cylinder 400, theinlets are closed as O rings come in physical contact with walls of theremaining portion of the first cylinder 400. In one embodiment,positioning of the O rings on the first piston 500 and the dimensions ofthe lower end portion 404 may be such that with the rotation of thecrankshaft 602 by 30 degrees from the starting point of the crankshaft602, the gas chamber 510 is replenished with the atmospheric air.

Further, the fastener driving apparatus 10 may include at least onesensor such as a first sensor 3002 and a second sensor 3004, configuredto detect at least one position of the operation cycle and communicatethe detected position of the operation cycle to the control circuit. Asensor, such as a first sensor 3002 and a second sensor 3004, may bedisposed anywhere within or on the apparatus that facilitates the sensorin determining the operation cycle of the apparatus. In a non-limitingembodiment, a first sensor 3002 and a second sensor 3004 are disposed onthe first cylinder 400. More specifically, the first sensor 3002 isdisposed on the upper end portion 402 of the first cylinder 400 and thesecond sensor 3004 is disposed on the lower end portion 404 of the firstcylinder 400. The sensors 3002 and 3004 are communicably coupled to thecontrol circuit 200. The sensors 3002 and 3004 are communicably coupledto the control circuit 200 by means of various wired or wireless meansknown to the person skilled in the art. Further, in an embodiment, thesensors 3002 and 3004 are configured to detect at least one position ofthe first piston 500. More specifically, the first sensor 3002 isconfigured to detect position of the first piston 500 when the firstpiston 500 approaches the TDC of the first cylinder 400. Similarly, thesecond sensor 3004 is configured to detect position of the first piston500 when the first piston 500 approaches the BDC of the first cylinder400. Further, the first sensor 3002 and the second sensor 3004 areconfigured to communicate the detected position of the first piston 500to the control circuit 200. Based on the detected position by the sensor3004, the control circuit 200 is configured to disconnect the powersource 100 from the motor 300 to stop the operation cycle. It will beapparent that at least one sensor 3000 of the present disclosure may beconfigured at any location in or on the apparatus that causes the sensordiscern a position of a component or components of the apparatus fordetermining a position of the operation cycle of the apparatus. In oneembodiment, the control circuit 200 is configured to actuate the valvearrangement 2000 to configure one of the open position and the closedposition based on the detected position of the first piston 500.

The sensors 3002 and 3004 may be selected from, but not limited to, oneof or a combination of a limit switch, a Hall Effect sensor, a photosensor, a reed switch, a timer and a current or voltage sensor withoutdeparting from the scope of the disclosure. The sensors 3002 and 3004may also include Hall sensors combined with at least one magnet. Thesensors 3002 and 3004 are shown as disposed on the upper end portion 402and the lower end portion 404 in FIG. 1, however this disposition shouldnot be considered limiting. In another embodiment, the pair of sensors3000 may also be disposed on the first piston 500.

Further, the valve arrangement 2000 is operationally disposed betweenthe first cylinder 400 and the second cylinder 700. The valvearrangement 2000 is disposed in a manner such that the valve arrangement2000 acts as a medium for communicating gas between the first cylinder400 and the second cylinder 700. The valve arrangement 2000 isconfigured to assume one of the open position and the closed position.The valve arrangement 2000 is configured to define a gas passageway 2005between the first cylinder 400 and the second cylinder 700 in the openposition. In one embodiment of the present disclosure, a volume of thegas passageway 2005 is less than 15% of the volume of the first cylinder400. The volume of the gas passageway 2005 may be less than 15% of thevolume of the first cylinder 400 for minimizing losses related toaccumulation of the gas in the gas passageway 2005, and therebyincreasing the efficiency of the fastener driving apparatus 10. Thevalve arrangement 2000 is configured to block the gas passageway 2005 inthe closed position of the valve arrangement 2000.

The valve arrangement 2000 includes a valve spool 2006 and a valve body2008. The valve spool 2006 is slidably disposed in the valve body 2008.The valve spool 2006 may include an elongated groove 2010 configured ona central portion thereof. Further, in one embodiment of the presentdisclosure, the valve spool 2006 may be held in position by means of aspring (not shown) and pressure balance between two o-rings (not shown).The valve body 2008 may further include an vent opening 2012 configuredthereon. In the closed position of the valve arrangement 2000, the ventopening 2012 is configured to receive gas from the elongated groove 2010and pass the gas to atmosphere.

The valve arrangement 2000 assumes the open position and the closedposition by utilizing a coupling member 2050. The coupling member 2050is operably coupled between the motor 300 and the valve arrangement2000. In one embodiment, the coupling member 2050 may be operativelyconnected between the speed reduction mechanism 4000 and the valve spool2006. The coupling member 2050 is configured such that it imparts alinear movement to the valve spool 2006 in response to the rotationmovement of the motor 300 for covering/uncovering the opening 408,thereby defining the gas passageway 2005. Accordingly, the valvearrangement 2000 may assume the open position or the closed position.

In one embodiment, the coupling member 2050 may include a cam 2052, apushrod 2054, a rocker arm 2056 and a cam guide 2066. In one form, thecam 2052 may be coupled to the shaft 4002 that is coupled to the speedreduction mechanism 4000, so that the cam 2052 may rotate about axis ofthe shaft 4002. The pushrod 2054 operably couples the cam 2052 to therocker arm 2056. The rocker arm 2056 has a first arm 2058 and a secondarm 2060. The first arm 2058 is connected to a rear portion of the valvespool 2006 and the second arm 2060 is connected to the pushrod 2054. Thefirst arm 2058 and the second arm 2060 are pivotally connected to eachother at a pivot point 2062. Further, the second arm 2060 is alsopivotally connected to the pushrod 2054. The cam guide 2066 guides theupward and downward movement of the pushrod 2054.

The cam 2052 has a suitable profile such that with the rotation of thecam 2052, the pushrod 2054 is moved towards and away from the shaft 4002and acts on the rocker arm 2056 such that the rocker arm 2056 actuatesthe valve spool 2006 for the valve arrangement 2000 to assume the openposition and the closed position. In one form, the cam 2052 has aprofile having two rises and two falls in 360 degrees rotation about theshaft 4002 in one operation cycle. When the pushrod 2054 is pushed awayfrom the shaft 4002, the pushrod 2054 pushes the second arm 2060 torotate in a clockwise manner about the pivot point 2062. Due to theclockwise rotation of the second arm 2060 about the pivot point 2062,the first arm 2058 pulls the valve spool 2006 away from the opening 408and compresses a valve spool return spring 2064. Accordingly, the valvespool 2006 unblocks the opening 408, thereby causing the valvearrangement 2000 to assume the open position.

Further, with the rotation of the cam 2052 and due to a fall profile ofthe cam 2052, the pushrod 2054 comes towards the shaft 4002, therebycausing the second arm 2060 to make a counter clockwise rotation aboutthe pivot point 2062. Further, the first arm 2058 moves away from thevalve spool return spring 2064, which is in compressed state. Therelease of the valve spool return spring 2064 further helps the valvespool 2006 to come toward the opening 408 and thereby closes the opening408. Accordingly, the valve arrangement 2000 assumes the closedposition. In one embodiment, the valve spool 2006 includes a slot 2070configured in the rear portion of the valve spool 2006. In thisembodiment, the valve spool return spring 2064 which is in compressedstate when the valve arrangement 2000 is in open position, expands andpushes the valve spool 2006 to cover the opening 408. In thisembodiment, the first arm 2058 moves within the slot 2070. The slot 2070provides the valve spool 2006 for lost motion control as the valve spool2006 opens at high speed in relation to speed of the rocker arm 2056.More specifically, the slot 2070 allows the valve spool 2006 to openrapidly after the valve spool 2006 is tripped by the rocker arm 2056.

In one embodiment of the present disclosure, the valve arrangement 2000has a flow coefficient (Cv) greater than one. The flow coefficientdescribes the relationship between the pressure drop across a valve andcorresponding flow rate. A valve arrangement having higher flowcoefficient provides a larger flow of gas through valve arrangement at agiven pressure drop. Further, the valve arrangement 2000 is configuredas a snap acting valve. The snap acting valve may be defined as a valvethat has an opening time of less than 20 milliseconds. Herein, theopening time of the valve represents a time involved in opening of thevalve from the initial closed position to a position at which about 70percent of full flow of the compressed gas in the valve may be achieved.

The second cylinder 700 is pneumatically connected to the first cylinder400 via the valve arrangement 2000. The second cylinder 700 ispositioned parallel to the first cylinder 400. The second cylinder 700acts as an expansion cylinder, where the compressed gas within the firstcylinder 400 is allowed to expand when the valve arrangement 2000assumes the open position after the compression stroke of the firstpiston 500. The second cylinder 700 includes a proximal end portion 702,a distal end portion 704 and a top plate 706. Further, a bumper 708 maybe disposed in the distal end portion 704 of the second cylinder 700.The bumper 708 is configured to absorb excess energy at the end of anexpansion stroke, i.e., when the anvil 900 strikes the fastener 1000.The bumper 708 may be composed of various impact energy absorbingmaterials, such as an elastomer, and the like.

The second piston 800 is disposed within the second cylinder 700. Thesecond piston 800 is configured to reciprocally move within the secondcylinder 700. The anvil 900 is coupled to a rear face 804 of the secondpiston 800 by means of a connector 806 coupled to the rear face 804. Theconnector 806 may be coupled to the rear face 804 by means of variousmeans and mechanisms, such as a nut and bolt arrangement, a rivet,welding and other arrangements known in the art. The anvil 900 may besecured in a central groove (not shown) of the connector 806, by use ofsuitable means, such as a nut and bolt arrangement, a rivet, welding,and the like known in the art. Further, in one embodiment of the presentdisclosure, the connector 806 and the anvil 900 may also be configuredas a single unit.

The anvil 900 is configured to reciprocally move along with the secondpiston 800. The anvil 900 is capable of linearly moving within thesecond cylinder 700 and a fastener guide 1010. Further, the anvil 900 iscapable of striking the fastener 1000 to drive the fastener 1000 intothe workpiece. The fastener guide 1010 is configured to receive thefastener 1000 from a fastener feeder 1020.

Further, in one embodiment of the present disclosure, the secondcylinder 700 may further include a second bumper disposed on theproximal end portion 702 of the second cylinder 700 for absorbing excessenergy when the second piston 800 is retracted to its initial position.Furthermore, in one embodiment of the present disclosure, the secondcylinder 700 may include an o-ring or a recess in the top plate 706 formaintaining the second piston 800 and the anvil 900 to their initialpositions (pre-fastener driving positions as shown in FIG. 1). Moreover,in one embodiment of the present disclosure, the second cylinder 700 mayinclude a magnet disposed on the top plate 706 and a piece of ferrousmaterial in the anvil 900 for maintaining the second piston 800 and theanvil 900 to their initial positions. Accordingly, by maintaining thesecond piston 800 and the anvil 900 in their upper positions andensuring that there is little or no extra dead volume between the secondpiston 800 and the top plate 706, maximum efficiency may be achieved asthe expansion of the gas after the compression stroke acts directly onthe second piston 800. Further, such arrangement precludes anyaccidental release of the anvil 900 and thereby facilitates more safetyto the user.

The operation cycle of the fastener driving apparatus 10 is shown in aprogressive manner in FIGS. 1 to 8, and will now be described withreference to FIGS. 1 to 8.

Referring again to FIG. 1, a first stage of the operation cycle of thefastener driving apparatus 10 is shown. At this stage of the operationcycle, the first piston 500 is at the BDC of the first cylinder 400, andthe second piston 800 and the anvil 900 are at the proximal end portion702 of the second cylinder 700, the valve arrangement 2000 is in theclosed position, the fastener 1000 is disposed in the fastener guide1010 and the motor 300 is in an OFF state. Positioning of the secondpiston 800 and the anvil 900 at the proximal end portion 702 represent‘initial positions’ of the second piston 800 and the anvil 900 at thebeginning of the operation cycle. As the first piston 500 is at the BDC,the vertical actuation member 5000 keeps the check valve 508 in the openposition. In the open position of the check valve 508, the atmosphericair gets filled in the gas chamber 510 from the check valve 508 as shownby arrows ‘A1’ in FIG. 1. Alternatively, in another embodiment of thepresent disclosure, the atmospheric air may be filled in the gas chamber510 by means of the series of holes or the enlarged opening configuredin the lower end portion 404 of the first cylinder 400. Further, thecheck valve 508 in its closed position prevents any exit of gas from thegas chamber 510.

Further, for initiating the operation cycle of the fastener drivingapparatus 10, the user may actuate the switch 302. The control circuit200 by means of the second sensor 3004 ensures that the first piston 500is at the BDC of the first cylinder 400. After ensuring that the firstpiston 500 is at the BDC of the first cylinder 400, the control circuit200 actuates the power source 100 to supply power to the motor 300. Themotor 300 then drives the linear motion converter 600, which in turnfacilitates the first piston 500 to execute the compression stroke. Thevalve arrangement 2000 is in the closed position and the first piston500 moves from the lower end portion 404, i.e., BDC of the firstcylinder 400 towards the upper end portion 402, i.e., TDC of the firstcylinder 400. Further, as the first piston 500 moves towards the TDC,the vertical actuation member 5000 causes the check valve 508 to assumethe closed position. More specifically, due to a pressure difference onboth sides of the check valve 508 (inside and outside of the firstcylinder 400), the check valve 508 is configured to assume the closedposition. Further, as valve arrangement 2000 is in the closed position,the first piston 500 compresses the gas in the gas chamber 510. Duringthe compression stroke, due to the cam rise profile of the cam 2052 thatis rotating, the second arm 2060 starts rotating in the clockwisedirection about the pivot point 2062. Accordingly, the first arm 2058starts pulling the valve spool 2006 rearward in order to uncover theopening 408. Further, the valve spool return spring 2064 also startscompressing as the valve spool 2006 moves rearward.

Further, as shown in FIG. 2, as the first piston 500 reaches the TDC ofthe first cylinder 400, the gas is compressed to a predeterminedpressure. In one embodiment of the present disclosure, for driving astandard 18 gages and 2 inches long fastener 1000, the gas in the gaschamber 510 may be compressed to a predetermined pressure of 160 psi(pounds per square inch) with a volume of the compressed gas beingapproximately one cubic inch. The first piston 500 is configured tocompress the gas in the gas chamber 510 at the predetermined pressure ina single rapid linear stroke, i.e., the compression stroke. Bycompressing the gas in the gas chamber 510 in the single rapid linearstroke, the gas is compressed in a way such that the pressure of thecompressed gas exceeds a pressure that will be predicted by the formulaP1V1=P2V2. Herein, P1 and P2 represent pressure of the gas and V1 and V2represent volume of the gas. Such increase in the pressure may bemodeled with a compression exponent greater than 1.05. Compressionexponents greater than 1.05 yield higher gas pressures for a givencompression ratio than the gas pressure for a compression done in anormal manner. More specifically, such a compression exponent allowsmore energy to be stored in the compressed gas than the energy stored ifthe compression were done via a normal multi-stroke compressor (in whichthe heat of compression may be lost to the environment.)

A formula for compression exponent greater than 1.05 may be written as:PV^(n)=K, where P is pressure of the compressed gas, V is volume of thecompressed gas, n is the compression exponent and K is a constant. Forair in an isothermal compression, the compression exponent is 1.05, andfor an adiabatic compression the compression exponent is about 1.4. Inan embodiment of the present disclosure, as the compression cycle issufficiently short, the gas in the gas chamber 510 may be compressed tothe predetermined pressure at a compression exponent of approximately atleast 1.1.

Further, as the first piston 500 reaches towards the TDC of the firstcylinder 400, due to the rise profile of the rotating cam 2052, thesecond arm 2060 continues rotating in the clockwise direction about thepivot point 2062. Accordingly, the first arm 2058 pulls the valve spool2006 rearward in order to uncover the opening 408 for configuring theopen position of the valve arrangement 2000, which is shown in FIGS. 3and 4.

Now referring to FIG. 3 and FIG. 4, next stages of the operation cycleare shown. Particularly as shown in FIG. 3, the valve arrangement 2000assumes the open position after completion of the compression stroke. Asthe valve arrangement 2000 is in the open position, the compressed gasat the predetermined pressure in the first cylinder 400 is communicatedto the second cylinder 700 through the gas passageway 2005. Thecompressed gas is then allowed to expand in the second cylinder 700causing the second piston 800 and the anvil 900 to move linearly in adownward direction. Further, the anvil 900 extends along a longitudinalaxis of the second cylinder 700 into the fastener guide 1010 forstriking the fastener 1000. The anvil 900, upon striking the fastener1000, is capable of driving the fastener 1000 into the workpiece asshown in FIG. 4.

As the compressed gas from the first cylinder 400 is rapidlycommunicated to the second cylinder 700 through the gas passageway 2005,such rapid communication of the compressed gas from first cylinder 400to the second cylinder 700 yields a rapid acceleration of the secondpiston 800 and the anvil 900 in the downward direction. Such rapidacceleration of the second piston 800 and the anvil 900 results in aquick fastener drive stroke with a low reaction force. Additionally, thelinear movement of the anvil 900 through the fastener guide 1010 enablesin jam clearing of the fastener guide 1010. Such jam clearing removesthe fastener fragments or other debris inside the fastener guide 1010and thereby avoids the need of any manual operation for cleaning thefastener guide 1010. Accordingly, this would automatically make thefastener guide 1010 ready for a next operation cycle of driving thefastener 1000.

After the fastener 1000 is fully driven into the workpiece, the valvearrangement 2000 is configured to assume the closed position. Due to thefall profile of the rotating cam 2052, the second arm 2060 is free torotate in the counter clockwise direction about the pivot point 2062.Further, the valve spool return spring 2064 which is in the compressedstate during the open position of the valve arrangement 2000, startsexpanding and thereby pushes the valve spool 2006 forward in order tocover the opening 408. Accordingly, the valve arrangement 2000 assumesthe closed position, as shown in FIG. 5. Further, due to continuousrotation of the motor 300, the first piston 500 is configured to executethe return stroke. During the return stroke, the first piston 500 movesdownwardly from the upper end portion 402, i.e., the TDC of the firstcylinder 400 towards the lower end portion 404, i.e., the BDC of thefirst cylinder 400. Further, due to the closed position of the valvearrangement 2000 and the closed position of the check valve 508, avacuum is created between the TDC of the first cylinder 400 and thefirst piston 500. More specifically, the vacuum is created between theupper face 502 of the first piston 500 and the cylinder end cap 406.

Further, as shown in FIG. 5, excess gas in the second cylinder 700 maybe vented to the atmosphere. The excess gas in the second cylinder 700may be vented to the atmosphere by means of the elongated groove 2010 ofthe valve spool 2006 and the vent opening 2012 configured on the valvebody 2008. Accordingly, such venting of the excess gas in the secondcylinder 700 facilitates reduction of gas pressure above the front face802 of the second piston 800. Furthermore, in the case that the movementof the first piston 500 is impeded to any extent, such venting releasesthe pressure on the second piston 800 and the anvil 900, thus providingsafety to the user.

Further, as shown in FIG. 6, during the return stroke of the firstpiston 500, when the first piston 500 reaches a predetermined position,the vacuum created within the first cylinder 400 is sufficient such thatthe second piston 800 and the anvil 900 may be retracted to theirinitial positions (as shown in FIG. 1), if the vacuum is communicated tothe second cylinder 700. Accordingly, when the first piston 500 reachesthe predetermined position in the first cylinder 400, the rocker arm2056 continues rotating in the clockwise direction about the pivot point2062 due to the cam rise profile of the rotating cam 2052. Accordingly,the first arm 2058 pulls the valve spool 2006 rearward in order touncover the opening 408 for configuring the open position of the valvearrangement 2000, which is shown in FIG. 7.

Further, a next stage of the operation cycle is illustrated in FIG. 7.The first arm 2058 pulls the valve spool 2006 rearward and uncovers theopening 408 configured on the cylinder end cap 406 of the first cylinder400 to configure the open position of the valve arrangement 2000.Thereafter, the vacuum created in the first cylinder 400 is communicatedto the second cylinder 700. More specifically, the vacuum created in thefirst cylinder 400 is filled by the gas communicated from the secondcylinder 700, when the valve arrangement 2000 assumes the open position.

Furthermore, as shown in FIG. 8, the vacuum communicated to the secondcylinder 700 causes the second piston 800 and the anvil 900 to retractto their initial positions. Further, as the first piston 500 isconfigured to reach to the BDC of the first cylinder 400, the secondpiston 800 and the anvil 900 are returned to their initial positions. Itwould be apparent to those skilled in the art that the second piston 800and the anvil 900 are retracted to their initial positions withoututilizing any drive energy of the fastener driving apparatus 10.Further, a person skilled in the art would appreciate that virtually allenergy from the fastener driving apparatus 10 is utilized to drive thefastener 1000 into the workpiece, as the retraction of the second piston800 and the anvil 900 is performed automatically as the first piston 500moves towards the BDC of the first cylinder 400 during the returnstroke. More specifically, the return of the second piston 800 and theanvil 900 is vacuum actuated, and does not utilize any energy used fordriving the fastener 1000.

Hence, a person skilled in the art would appreciate that the vacuumgenerated in the first cylinder 400 acts as ‘the retracting mechanism’in the fastener driving apparatus 10 of the present disclosure. It wouldbe apparent to those skilled in that art that the anvil 900 of thepresent disclosure do not require any specific retracting mechanism suchas compressing an anvil return spring or a bungee, the fastener drivingapparatus 10 of the present disclosure increases the drive speed of thepresent disclosure. Further, the kinetic energy caused by the axialmovement of the second piston 800, the connector 806 and the anvil 900is absorbed by the bumper 708.

As the second piston 800 and the anvil 900 reach to their initialpositions, the valve arrangement 2000 is configured to assume the closedposition as shown in FIG. 1. When the first piston 500 reaches the BDCof the first cylinder 400, the second sensor 3004 detects the presenceof the first piston 500 at the BDC, and the control circuit 200 receivesthe detected position from the second sensor 3004. Further, the controlcircuit 200 is configured to disconnect the power source 100 from themotor 300 to stop the operation cycle based on feedback from the secondsensor 3004. More specifically, the control circuit 200 disconnects thepower from the power source 100 to the motor 300 so that motor 300 stopsactuating the linear motion converter 600 for linearly moving the firstpiston 500 inside the first cylinder 400. In one embodiment of thepresent disclosure, the motor 300 may be stopped by means of dynamicbraking mechanism. It would be apparent to those ordinary skilled in theart that in this condition, the fastener driving apparatus 10 is in aready position for performing a next operation cycle of the fastenerdriving operation. Accordingly, in a single stroke of the first piston500 the operation cycle of the fastener driving is completed by thefastener driving apparatus 10. Accordingly, with each triggering (i.e.,powering of the switch 302), one fastener, such as the fastener 1000, isdriven into the workpiece. It would be apparent to those ordinaryskilled in the art that in case of continuous driving of fasteners 1000,the motor 300 may be continued as running in order to execute thesuccessive operation cycles in a continuous manner.

Referring now to FIG. 9, in another embodiment of the present invention,a fastener driving apparatus 20 having a valve arrangement such as avalve arrangement 6000 and a coupling member such as a coupling member6050, is shown. The valve arrangement 6000 includes a valve spool 6010,which has a cam ramp 6012 configured on a rear portion 6014 of the valvespool 6010. The rear portion 6114 of the valve arrangement 6000 is alsooperably coupled to a valve spool return spring such as the valve spoolreturn spring 2064.

The coupling member 6050 includes a cam such as the cam 2052, a pushrod6052 and a cam guide such as the cam guide 2066. The pushrod 6052 isoperatively coupled to the cam 2052. With the rotation of the cam 2052,the pushrod 6052 executes an upward and downward movement, i.e., towardsand away from the shaft 4002. As shown in FIG. 9, the pushrod 6052 actsagainst a cam ramp 6012 on the valve spool 6010 to configure the openposition or the closed position of the valve arrangement 2000. The valvespool return spring 2064 also aids in closing the opening 408 when thepushrod 6052 retracts, i.e., goes towards the shaft 4002.

For example, as shown in FIG. 9, due to variable profile of the cam2052, when the pushrod 6052 is in contact with the cam ramp 6012 at apoint 6016, the valve arrangement 6000 is in the closed position. Due tothe cam rise profile of the cam 2052, the pushrod 6052 is driven in theupward direction, i.e., away from the shaft 4002. As the pushrod 6052acts against the cam ramp 6012 to proceed in the upward direction, aresultant force is applied that pushes the valve spool 6010 in therearward direction in order to uncover the opening 408 (when the pushrod6052 is in contact with the cam ramp 6012 at a point 6018). Due to this,the valve arrangement 6000 assumes the open position and simultaneouslythe valve spool return spring 2064 also compresses. It would be apparentto those skilled in the art that in an operation cycle, the cam 2052will rotate by 360 degrees, and the cam 2052 will have a profile havingtwo rises and two falls.

Referring now to FIG. 10, yet another embodiment of the presentinvention having a valve arrangement such as a valve arrangement 7000utilized in a fastener driving apparatus 30, is shown. The fastenerdriving apparatus 30 does not utilize any coupling member such as thecoupling member 2050 operatively coupled between the valve arrangement7000 and the motor 300.

The valve arrangement 7000 may include a pneumatic valve 7002 and avalve solenoid 7004. The valve solenoid 7004 is configured to actuatethe pneumatic valve 7002. The pneumatic valve 7002 includes a valvespool 7006 and a valve body 7008. The valve spool 7006 is slidablydisposed in the valve body 7008. The valve spool 7006 may include anelongated groove 7010 configured on a central portion thereof. Further,in one embodiment of the present disclosure, the valve spool 7006 may beheld in position by means of a spring (not shown) and pressure balancebetween two o-rings (not shown). The valve body 7008 may further includea vent opening 7012 configured thereon. In the closed position of thevalve arrangement 7000, the vent opening 7012 is configured to receivegas from the elongated groove 7010 and pass the gas to atmosphere.

Further, the valve solenoid 7004 includes an actuating member 7014, asolenoid return spring 7016, and a solenoid member 7018. The actuatingmember 7014 is configured to actuate the valve spool 7006 to configureone of the closed position and the open position of the valve spool7006. The solenoid return spring 7016 is functionally coupled to theactuating member 7014. The solenoid member 7018 is configured to actuatethe actuating member 7014 and the solenoid return spring 7016 such thatthe valve spool 7006 may assume one of the open position and the closedposition. The solenoid member 7018 is electrically coupled to thecontrol circuit 200 that is configured to actuate the solenoid member7018. The solenoid member 7018 may be electrically coupled to thecontrol circuit 200 by means of wired, wireless or any other means knownin the art. The control circuit 200 may actuate the solenoid member 7018for configuring the valve arrangement to assume one of the open positionand the closed position based on the position of the first piston 500detected within the first cylinder 400 and timings of start and stop ofan operation cycle of the fastener driving apparatus 30.

More specifically, for configuring the open position of the valvearrangement 7000, i.e., the open position of the valve spool 7006, thesolenoid member 7018 actuates the actuating member 7014. Further, theactuating member 7014 moves the valve spool 7006 towards the solenoidmember 7018 and unblocks the opening 408 configured on the cylinder endcap 406 of the first cylinder 400. More specifically, once the valvespool 7006 is cracked open by the solenoid member 7018, the gas pressuremay act on a front face (not shown) of the valve spool 7006 and movesthe valve spool 7006 towards the solenoid member 7018 very fast andsnaps the valve spool 7006 to assume the open position. While moving thevalve spool 7006 towards the solenoid member 7018, the actuating member7014 compresses the solenoid return spring 7016. Further, the solenoidmember 7018 is configured to retain the open position of the valve spool7006 even when the pressure in the gas chamber 510 drops. Suchcharacteristics of the solenoid member 7018 to retain the open positionof the valve spool 7006 even when the pressure in the gas chamber 510drops, increases efficiency of the valve arrangement 7000 andfacilitates a complete driving of the fastener 1000 into the workpiece.Further, the opening force required for configuring the open position ofthe valve arrangement 7000 is at least 1.5 times of the force requiredfor maintaining the closed position of the valve arrangement 7000.

Similarly, for configuring the closed position of the valve arrangement7000, i.e., the closed position of the valve spool 7006, the solenoidmember 7018 actuates the actuating member 7014 to move towards thesecond cylinder 700 by means of release of potential energy stored inthe solenoid return spring 7016. Accordingly, the actuating member 7014moves the valve spool 7006 towards the second cylinder 700, and therebyblocks the opening 408 configured on the cylinder end cap 406 of thefirst cylinder 400.

It would be apparent to those skilled in the art that the valvearrangement 700 may be configured to assume the open position or theclosed position based on the signal received from the control circuit200. For example, during the compression stroke of the compressionstroke of the operation cycle, when the first piston 500 reaches the TDCof the first cylinder 400, the first sensor 3002 detects the position ofthe first piston 500 and communicates the detected position of the firstpiston 500 to the control circuit 200. Thereafter, the control circuit200 actuates the solenoid member 7018 of the valve arrangement 7000. Thesolenoid member 7018 then actuates the actuating member 7014 forconfiguring the open position of the valve spool 7006. Similarly, duringthe return stroke of the operation cycle, positioning of the firstpiston 500 at the predetermined position may be detected by the secondsensor 3004. More specifically, the second sensor 3004 is configured todetect the predetermined position of the first piston 500 on the returnstroke so as to control the timing when the valve arrangement 7000should assume the open position. The second sensor 3004 communicatesthis detected position of the first piston 500 to the control circuit200. Further, the control circuit 200 actuates the solenoid member 7018to configure the open position of the valve arrangement 7000. Further,as the valve arrangement 7000 assumes the open position, the vacuum isutilized to retract the second piston 800 and the anvil 900 to theirinitial positions in the second cylinder 700.

Although in the present embodiment of the present disclosure, the valvearrangement 7000 includes the valve solenoid 7004 for configuring theopen position and the closed position of the valve arrangement 7000, thepresent disclosure is not limited to this particular arrangement only.In another embodiment of the present disclosure may include a valvearrangement having a pneumatic valve, similar to the pneumatic valve7002 actuated by a plurality of sensors. Such valve arrangement may bedesigned by considering various parameters such as pressure drop throughthe valve arrangement, the opening time of the valve arrangement, andthe volume of gas contained in a gas passageway of the valvearrangement.

Various embodiments of the present disclosure offer followingadvantages. The fastener driving apparatus, such as the fastener drivingapparatuses 10 10, 20 and 30, utilizing valve arrangements such as valvearrangements 2000, 6000 and 7000, respectively. Such fastener drivingapparatuses, as described herein, provide retracting mechanisms thatprecludes consumption of drive energy of the fastener drivingapparatuses and facilitates a fastener to be fully driven into aworkpiece. Further, the retracting mechanisms of the fastener drivingapparatuses of the present disclosure are capable of providing moresafety to a user. Furthermore, the retracting mechanisms precludereduction of drive speed of the fastener driving apparatuses. Moreover,the fastener driving apparatuses of the present disclosure are portablein nature. Further, the fastener driving apparatuses are inexpensive.Furthermore, the fastener driving apparatuses are simple inconstruction. Still further, the fastener driving apparatuses arecapable of minimizing reactionary force and thereby providing morecomfort to the user. Additionally, the fastener driving apparatus arecapable of driving the fastener into the workpiece in a single stroke.

The foregoing descriptions of specific embodiments of the presentdisclosure have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent disclosure to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the present disclosure and its practicalapplication, and to thereby enable others skilled in the art to bestutilize the present disclosure and various embodiments with variousmodifications as are suited to the particular use contemplated. It isunderstood that various omissions and substitutions of equivalents arecontemplated as circumstances may suggest or render expedient, but suchomissions and substitutions are intended to cover the application orimplementation without departing from the spirit or scope of the claimsof the present disclosure.

1. A fastener driving apparatus for driving a fastener into a workpiece,the fastener driving apparatus comprising: a power source; a controlcircuit electrically coupled to the power source; a motor electricallycoupled to the power source and responsive to the control circuit; afirst cylinder; a first piston reciprocally movable within the firstcylinder to execute a compression stroke and a return stroke in anoperation cycle of driving the fastener into the workpiece, the firstpiston defining a gas chamber within the first cylinder, the gas chambercapable of accommodating gas therein; a linear motion converter drivenby the motor and operationally coupled to the first piston forreciprocally moving the first piston within the first cylinder; a secondcylinder pneumatically connected to the first cylinder; a second pistonreciprocally movable within the second cylinder; an anvil coupled to thesecond piston, the anvil capable of striking the fastener to drive thefastener into the workpiece; a valve arrangement operationally disposedbetween the first cylinder and the second cylinder for pneumaticallyconnecting the first cylinder and the second cylinder, the valvearrangement configured to define a gas passageway between the firstcylinder and the second cylinder in an open position and blocking thegas passageway in a closed position; and at least one sensorelectrically coupled to the control circuit, the at least one sensorconfigured to detect at least one position of the operation cycle andcommunicate the detected position of the operation cycle to the controlcircuit, wherein during the compression stroke, the first piston isconfigured to move towards a top dead center of the first cylinder forcompressing the gas in the gas chamber, the valve arrangement assumingthe open position for communicating the compressed gas to the secondcylinder causing the second piston to move linearly and enabling theanvil to drive the fastener into the workpiece; and wherein during thereturn stroke the valve arrangement assumes the closed position and thefirst piston is configured to move towards a bottom dead center of thefirst cylinder thereby creating a vacuum in the first cylinder betweenthe top dead center of the first cylinder and the first piston; andwherein at a predetermined position of the first piston during thereturn stroke the valve arrangement assumes the open position, therebycommunicating the vacuum created in the first cylinder to the secondcylinder and causing the second piston and the anvil to retract toinitial positions of the second piston and the anvil; and wherein duringthe return stroke, based on the at least one detected position by the atleast one sensor, the control circuit is configured to disconnect thepower source from the motor to stop the operation cycle.
 2. The fastenerdriving apparatus of claim 1, wherein the power source is a rechargeablebattery.
 3. The fastener driving apparatus of claim 1, wherein thelinear motion converter comprises a crankshaft mechanism.
 4. Thefastener driving apparatus of claim 1, wherein in the open position ofthe valve arrangement, a compression valve has a flow coefficientgreater than one.
 5. The fastener driving apparatus of claim 1, whereinduring the compression stroke of the first piston the gas in the gaschamber is compressed to the predetermined pressure at a compressionexponent greater than 1.05.
 6. The fastener driving apparatus of claim1, wherein the valve arrangement comprises a valve solenoid.
 7. Thefastener driving apparatus of claim 1, wherein a valve is adapted toallow atmospheric air to flow into the gas chamber after the vacuum hasbeen communicated to from the first cylinder to the second cylinder. 8.The fastener driving apparatus of claim 7 further comprising anactuation member disposed on a body portion of the fastener drivingapparatus for actuating the valve to allow the atmospheric air to flowinto the gas chamber.
 9. The fastener driving apparatus of claim 1,wherein volume of the gas passageway is less than about 15% of volume ofthe first cylinder.
 10. The fastener driving apparatus of claim 1,further comprising a coupling member coupled between the motor and thevalve arrangement, the coupling member actuated by the rotation of themotor for actuating the valve arrangement to: assume the open positionfor communicating the compressed gas to the second cylinder during thecompression stroke; assume the closed position for creating a vacuum inthe first cylinder between the top dead center of the first cylinder andthe first piston during the return stroke; and assume the open positionfor communicating the vacuum from the first cylinder to the secondcylinder during the return stroke.
 11. The fastener driving apparatus ofclaim 1, wherein the control circuit is further configured to actuatethe valve arrangement to assume the closed position after the vacuumcreated in the first cylinder is communicated to the second cylinder.12. The fastener driving apparatus of claim 1, wherein the valvearrangement comprises a pneumatic valve and a valve solenoid foractuating the pneumatic valve, the valve solenoid controlled by thecontrol circuit.
 13. The fastener driving apparatus of claim 1, whereinthe valve arrangement comprises a vent opening for releasing gas fromthe second cylinder to atmosphere in the closed position of valvearrangement.
 14. A fastener driving apparatus for driving a fastenerinto a workpiece, the fastener driving apparatus comprising: a powersource; a control circuit electrically coupled to the power source; amotor electrically coupled to the power source and responsive to thecontrol circuit; a first cylinder; a first piston reciprocally movablewithin the first cylinder to execute a compression stroke and a returnstroke in an operation cycle of driving the fastener into the workpiece,the first piston defining a gas chamber within the first cylinder, thegas chamber capable of accommodating gas therein; a linear motionconverter driven by the motor and operationally coupled to the firstpiston for reciprocally moving the first piston within the firstcylinder; a second cylinder pneumatically connected to the firstcylinder; a second piston reciprocally movable within the secondcylinder; an anvil coupled to the second piston, the anvil capable ofstriking the fastener to drive the fastener into the workpiece; a valvearrangement operationally disposed between the first cylinder and thesecond cylinder for pneumatically connecting the first cylinder and thesecond cylinder, the valve arrangement configured to define a gaspassageway between the first cylinder and the second cylinder in an openposition and blocking the gas passageway in a closed position; and atleast one sensor electrically coupled to the control circuit, the atleast one sensor configured to detect at least one position of theoperation cycle and communicate the detected position of the operationcycle to the control circuit, wherein during the compression stroke, thefirst piston is configured to move towards a top dead center of thefirst cylinder for compressing the gas in the gas chamber, the valvearrangement assuming the open position for communicating the compressedgas to the second cylinder causing the second piston to move linearlyfrom a first position to a second position and enabling the anvil tomove from a first position to a second position to drive the fastenerinto the workpiece; and wherein during the return stroke the firstpiston is configured to move towards a bottom dead center of the firstcylinder, thereby creating a vacuum in the gas chamber at the top of thefirst cylinder, wherein said valve arrangement assumes an open positionduring at least a portion of the return stroke of the first piston,thereby communicating said vacuum through said valve arrangement to thesecond cylinder, which vacuum causes the second piston to move linearlyfrom said second position to said first position and the anvil to movefrom said second position to said first position; and wherein during thereturn stroke, based on the at least one detected position by the atleast one sensor, the control circuit is configured to disconnect thepower source from the motor to stop the operation cycle.
 15. Thefastener driving apparatus of claim 1, wherein the second cylinderfurther comprises a magnet disposed on a top plate thereof, and theanvil comprises a ferrous material.
 16. The fastener driving apparatusof claim 14, wherein the second cylinder further comprises a magnetdisposed on a top plate thereof, and the anvil comprises a ferrousmaterial.
 17. A fastener driving apparatus for driving a fastener into aworkpiece, the fastener driving apparatus comprising: a power source; acontrol circuit electrically coupled to the power source; a motorelectrically coupled to the power source and responsive to the controlcircuit; a first cylinder; a first piston reciprocally movable withinthe first cylinder to execute a compression stroke and a return strokein an operation cycle of driving the fastener into the workpiece, thefirst piston defining a gas chamber within the first cylinder, the gaschamber capable of accommodating gas therein; a linear motion converterdriven by the motor and operationally coupled to the first piston forreciprocally moving the first piston within the first cylinder; a secondcylinder pneumatically connected to the first cylinder; a second pistonreciprocally movable within the second cylinder; an anvil coupled to thesecond piston, the anvil capable of striking the fastener to drive thefastener into the workpiece; a valve arrangement operationally disposedbetween the first cylinder and the second cylinder for pneumaticallyconnecting the first cylinder and the second cylinder, the valvearrangement configured to define a gas passageway between the firstcylinder and the second cylinder in an open position and blocking thegas passageway in a closed position; and at least one sensorelectrically coupled to the control circuit, the at least one sensorconfigured to detect at least one position of the operation cycle andcommunicate the detected position of the operation cycle to the controlcircuit, wherein during the compression stroke, the first piston isconfigured to move towards a top dead center of the first cylinder forcompressing the gas in the gas chamber, the valve arrangement assumingthe open position for communicating the compressed gas to the secondcylinder causing the second piston to move linearly from a firstposition to a second position and enabling the anvil to move from afirst position to a second position to drive the fastener into theworkpiece; and wherein during the return stroke the first piston isconfigured to move towards a bottom dead center of the first cylinder,thereby creating a vacuum in the gas chamber at the top of the firstcylinder, wherein said valve arrangement assumes an open position duringat least a portion of the return stroke of the first piston, therebycommunicating said vacuum through said valve arrangement to the secondcylinder, which vacuum causes the second piston to move linearly fromsaid second position to said first position and the anvil to move fromsaid second position to said first position; and wherein based on the atleast one detected position by the at least one sensor, the controlcircuit is configured to stop the operation cycle.